Switching systems are used throughout the telecommunications industry for receiving and redirecting communications between parties. In a general configuration, a telecommunications switch interfaces with N trunks from one or more telephone service providers, and M trunks servicing one or more categories of equipment such as PBX's for office phone systems, other telecommunication switches, etc. A communication attempt received from one of the N trunks is then routed out an appropriate one of M trunks or vise versa.
In wireless telecommunications systems, such as paging systems, personal communication systems (PCS) and cellular systems, wireless switching systems are used for receiving and routing communications between parties. In general, the wireless switches perform the equivalent operations of long distance switches. During operation, a service provider receives a call setup attempt. If the call setup attempt is directed towards a number that is serviced by a wireless service provider, the call is routed to a wireless switching system operated by that wireless service provider.
One problem that wireless switching systems are confronted with is processing calls at a higher call flow rate than is required for non-wireless switching systems. In a typical non-wireless switching system, the maximum call flow rate or the worst case call flow rate is on the order of one call every 30 seconds. In normal operation (non-worst case), non-wireless switching systems are required to process calls at a rate of one call every 60 to 90 seconds. However, in wireless applications, especially in a paging system, the call flow rate is on the order of one call every 8 to 10 seconds. The increased call flow rate is due to the fact that the duration of a paging call is significantly less than the duration of a typical telephone call. Thus, current state of the art switching systems are not able to process calls at the flow rate required for typical wireless applications. Even current state of the art wireless switching systems are not able to process calls at these higher flow rates. This inadequacy of current state of the art switches results in increasing the number of blocked calls or unsuccessful call setup attempts. In order to alleviate blocked calls, service providers are forced to provide additional lines to adequately service their customers. Although this technique may reduce the number of blocked calls, it is an inefficient utilization of bandwidth. Therefore, there is a need in the art for a wireless switching system that meets the call flow demands of a wireless switching system while maintaining an efficient utilization of the bandwidth.
One problem that contributes to the inability of current state of the art switching systems to meet the call flow demands of a wireless communication system is the inefficient use and assignment of phone numbers within the telecommunications system. Until recently, phone numbers were sold in blocks of 100 (centi-records). Recently, due to fragmentation, this has been reduced to blocks of 10 (deca-records). The inefficiency of the current system is realized when attempting to receive a call at the switch and route it out the appropriate trunk.
In typical operation, each call received at a switch includes a destination identifying number or DID (direct inward dialing) number. The DID number identifies the called party, and thus, is examined to determine on which trunk to output the call from the switch. For instance, if a paging system is serviced by a single wireless switch, the DID of the received call is used to determine which output channels to route the call over.
In switching systems representing the state of the art, this is accomplished by assigning hunt groups to contiguous blocks of DID numbers. Each hunt group consists of one or more DSO channels (i.e., DSO 1-6) that are used to service a block of 100 DID numbers. The hunt groups are dedicated to blocks of DID numbers in this manner to reduce the amount of time required for forwarding the call. For example, a DID of 436-5024 will result in selecting a hunt group associated with all 100 numbers that start with 43650 (e.g., 436-5000 to 436-5099). Thus, the least significant numbers of the DID are masked off, and only the most significant digits must be examined to identify the correct hunt group. This results in reducing the amount of time required to examine the DID number and identify a hunt group.
The inefficiency of this technique is apparent when a switch operator is only able to purchase DID numbers in blocks of 10. This results in having a hunt group that is capable of servicing 100 DID numbers, being dedicated to a block of only 10 DID numbers. The inefficiency of this technique is even more apparent when the fragmentation of the numbers results in blocks of DID numbers that are less than 10.
One technique to resolve this problem is to assign DID numbers to hunt groups at a higher resolution (i.e., on a number by number basis). For instance, rather than masking off the insignificant digits of a DID number, the entire DID number can be examined and assigned to a hunt group. A problem associated with this technique is that the efficiency obtained by assigning blocks of contiguous DID numbers to a hunt group is lost. Thus, the amount of time required to identify the appropriate hunt group and route the received call accordingly results in the inability of the switch to meet the call flow requirements. Therefore, there is a need in the art for a switching system that can assign non-contiguous blocks of DID numbers to a hunt group and still meet the call flow requirements of the telecommunications system.
Another problem that contributes to the inability of current state of the art switching systems to meet the call flow demands of a wireless communication system is the techniques used to match DID numbers with hunt groups. Typical switching systems rely on the use of a host system, located external of the switching system, for performing this function. Thus, when a call and DID number is received, the external host must be queried with the DID number to identify the appropriate hunt group. The overhead associated with querying the external host contributes to the slow response time of the switching system in processing the call. Therefore, there is a need in the art for a switching system that eliminates or reduces the overhead associated with querying an external host to match a DID number with the appropriate hunt group.
Another problem that wireless switching systems are confronted with is the ability to provide true, ten digit portability of the DID numbers. The typical DID numbering scheme in the US consists of segmenting a ten digit number into three parts: (a) an area code ("NPA"); (b) a local exchange ("NXX"); and (c) a line serviced by the local exchange ("YYYY"). Thus, a ten digit DID number is represented as NPA-NXX-YYYY and can range over a domain of 10 billion possible numbers.
State of the art switching systems are limited to operate on a subset of the 10 billion domain of numbers available. Typically, a switching system is limited to a single NPA and NXX, thereby, limiting the possible numbers serviced by the switching system to 10,000 possible numbers. More typically, to be able to efficiently process the 10,000 possible numbers within a given NPA-NXX region, several switching systems will be utilized. Thus, any given switching system is only required to process blocks of the 10,000 available numbers, usually in block sizes of 100 or 10.
In today's telecommunications environment, this technique imposes significant design requirements in the design of the telecommunications system. Considerable effort is required to distribute the load of each switching system to ensure that a given switching system services as many contiguous blocks of DID numbers as possible.
In order to provide true, ten digit portability, a switching system must be able to process any of the possible 10 billion different numbers available. A switching system with this capability can be used to service numbers without being limited to a specific NPA-NXX. This would allow a single switch to process calls to an 800 number, local calls within a specific NPA-NXX area, and long distance calls with various NPA's and NXX's. This would allow greater flexibility in the design of the telecommunications system and reduce the cost for servicing various calling requirements. Therefore, there is a need in the art for a switching system that has the ability to perform true, ten digit portability of the DID numbers.
Another problem that wireless switching systems are confronted with is realized when a single switching system is used to route calls between various carriers using differing communication protocols and transmission characteristics. In general, each carrier can utilize its own communication protocol and generate its own timing characteristics for transmitting information. Thus, if a switching system is required to route a call from carrier A to carrier B, the switching system must route the call from carrier A, through a switching system compatible with carrier B. Carrier B usually charges a fee for providing this service. Thus, typical switching systems limit the variety of carriers that they service so that costs for routing the calls can be minimized. Therefore, there is a need in the art for a switching system that can communicate with any type of equipment or carrier without limitation.
Yet another problem that wireless switching systems are confronted with is the requirement to be reconfigured when the characteristics of the telecommunications system changes. State of the art switching systems are configured prior to going on line. Thus, the hunt groups for a switching system and DID numbers associated with the hunt groups are defined at the onset. Once the switching system goes on line, if one of the hunt groups is over burdened (i.e., is not able to process the required call flow) the switching system must be taken off-line and reconfigured. This results in downtime during which the customers can not be serviced and the service provider loses revenue. Thus, there is a need in the art for a switching system that can be configured in real-time while the switching system is operating within the telecommunications system.